This week’s question came from Katherine, who asked, “What invasive plants and animals exist in the Chesapeake Bay and how were they introduced?”

Invasive species are animals and plants that are not native to a certain area and harm the ecosystem they invade. There are as many as 200 invasive species present in the Chesapeake Bay watershed that are causing some serious issues in an already-stressed ecosystem.

Invasive species can be introduced in many ways. Some travel accidentally through human trade and tourism, while others are deliberately introduced.

Mute swans were introduced into North America in the late 1800s, mainly for the purpose of “decorations” for zoos, parks and private estates. The Chesapeake Bay region’s mute swan population formed when five swans escaped from an estate in Talbot County, Maryland, in 1962. By 1999, an estimated 4,500 mute swans were living in Maryland and Virginia.

Nutria were introduced to Maryland in 1943 to establish an experimental fur station at the Blackwater National Wildlife Refuge, but it proved to be unprofitable. The rest of the nutria from the project were released or escaped, leading to an overwhelming population of the marsh-dwelling rodents at the beginning of the 21st century.

Phragmites is thought to have been introduced from Eurasia in the 19th century by way of dry ballast from ships. Today it dominates many mid-Atlantic marshes.

Purple loosestrife was introduced to the U.S. from Eurasia in the early 1800s for ornamental and medicinal purposes, as well as via dry ballast dumped by foreign ships. It spread through inland canals, increased development, the sale of the plant for use in gardens and seed generation for bee forage.

Water chestnut was first found in the U.S. in 1859 in Massachusetts, but has since spread to other locations in the northeast. It is believed that water chestnut was introduced as an ornamental plant in ponds and spread from there. It was found in Baltimore County, Md., in 1955 and has gone through several cycles of eradication and reappearing since that time.

Like phragmites, zebra mussels were introduced to the United States via ballast water from European ships traveling from the Caspian and Black seas. The freshwater mussels were spotted in the Great Lakes in 1988 and have since spread to many other water bodies throughout the United States, including the Susquehanna River.

Come back next week to find out about the damage invasive species are causing and what is being done to solve it!

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Image: The invasive plant phragmites dominates many marshes in the mid-Atlantic region.